I have noticed that Ubuntu 14.04 LTS is vulnerable to the Logjam vulnerability. The main reason for this is the NSS library it is using (3.18). A fix has been releases for NSS 3.19. To test your web browser go to https://weakdh.org/To find out what version of NSS you are using, open firefox and go to about:support and search for NSS.

Ubuntu 15.10 has the patched version of NSS. I have seen no indication that NSS 3.19.1 will be backported to 14.04 or 15.04. Manually upgrading causes dependency issues.